High temperature grease compositions



United States Patent Ofiice 3,052,632 Patented Sept. 4, 1962 3,052,632HIGH TEMPERATURE GREASE COMPOSITIONS Donald E. Loefller, Walnut Creek,Califl, assignor to Shell Oil Company, a corporation of Delaware NoDrawing. Filed Feb. 11, 1959, Ser. No. 792,463 5 Claims. (Cl. 252-515)This invention relates to lubricating grease compositions. Moreespecially it relates to improved grease compositions especially usefulat elevated operating temperatures.

As lubricants are required to perform at higher and higher temperaturesbecause of increased speeds of engines and machines, the advent of jetpropulsion and atomic energy as sources of power, etc., it has becomeincreasingly difiicult to provide greases fulfilling the requirements ofsuch lubricants. In attempting to provide suitable greases, the art hasprogressed from the use of petroleum lubricant vehicles thickened withmetal soaps of long chain fatty acids to more thermally stable syntheticlubricating oils such as the aliphatic diesters, silicone polymers, etc.thickened with such soaps or inorganic materials, such as silica gels orclays. The progress of thickener research has not in general kept pacewith the development of lubricant vehicles. At operating temperatures ashigh as 400-450 F., there are few greases available which will retaintheir consistency and lubricity for any substantial period of time.

One of the prominent advances in the art of high temperature greaselubrication has comprised the provision of greases gelled with dyes orpigments, namely, indogen compounds, phthalocyanine compounds,anthr-aquinones, azines, and especially indanthrene compounds. The artof preparing greases from these particular classes of materials has notbeen developed. Consequently, the greases comprising such dyes normallyrequire excessive amounts of the gelling agent to produce the greasestructure.

It is an object of the present invention to provide improved greasecompositions. -It is another object of the present invention to providegrease compositions especially useful at high operating temperatures. Itis a particular object of the present invention to provide dye gelledgreases having a reduced dye requirement for a given grease consistency.It is a special object of the present invention to reduce the high costof dye gelled greases. Other objects will become apparent during thefollowing description of the invention.

Now, in accordance with the present invention, it has been found thatthe consistency of greases gelled with indanthrene compounds may bematerially increased by the incorporation of 2.5-20% by weight, based onthe grease, of diaryl amines having the general configuration whereineach Ar is an aromatic hydrocarbon radical of the group consisting ofphenyl naphthyl, alkylated phenyl and 'alkylated naphthyl radicals.

In further accordance with the invention, an additional unexpectedadvantage is obtained in the prolonged high temperature bearing life ofthe grease compositions. This is especially surprising in view of thefact that the diaryl amines .above are less thermally stable than theindanthrene dyes.

Another unexplainable feature of the invention is that the use ofdiarylamines to increase consistency appears to be restricted to greasesgelled with indanthrene compounds, since addition of the same amines togreases gelled with other high temperature gelling agents either had noeffect on consistency or actually softened the grease.

The chief benefit derived from the present invention comprises a drasticreduction in the cost of the subject greases. This is material since theprincipal gelling agent, namely, the dyes are extremely expensivematerials while the amines are far less costly. For example, theindanthrene dyes at the present time cost in the order of $11.00 a poundwhile the amines are currently priced at 60-70 cents a pound.Consequently, any reduction in the dye content of the grease by acorresponding addition of the amine results in an approximatetwenty-fold saving in grease thickener cost. However, not only is thiscost reduction a principal factor but also the unexpected improvement inbearing life caused by the presence of the large quantities of aminespresent constitutes an impressive improvement in lubricating greases ofthis particular class.

While the proportion of amine normally utilized for increasing theconsistency of the subject grease compositions is between 2.5 and about20% by weight thereof, another measure of the suitable proportions maybe expressed in terms of equivalents of dye per hundred grams of grease.The maximum effect is obtained if between about 0.02 and 0. 1equivalents of amine per hundred grams of grease is utilized, althoughsubstantial increases in consistency and in bearing life are obtainedwhen the proportion of amine is between about 0.005 and 0.2 equivalentsper one hundred grams of grease.

Suitable diaryl-amines include the following:

Phenyl-alpha-naphthylamine Phenyl beta-naphthylamine Diphenylamine Dialpha-naphthyl) amine Di(beta-naphthyl) amine (Alpha-naphthyl)(beta-naphthyl) amine Di(tert-butylphenyl) amine (Sec-amylphenylphenylamine (Methylphenyl naphthylamine Preferably, any alkylsubstituents on the aryl nuclei have 1-10 carbon atoms each.

The amines are preferably incorporated by homogenizing them with thefinished grease containing the principal thickening agent and thelubricating oil. However, the amines may be incorporated with thethickener at the time the grease is originally prepared or may bedispersed in lubricating oil prior to addition of the principal.thickening component.

The most effective dye for use in high temperature greases has beenfound to be the parent compound of the series, namely, indanthreneitself, but other indanthrene compounds may be employed. It is best toutilize the indanthrene compounds in their non-metallic form, that is,without neutralization of the carbonyl groups in said compounds withsuch ions as sodium or potassium, calcium, etc. While it is possible toemploy the partially or fully neutralized indanthrene compounds asgrease thickening agents, greases having maximum lubricating life atelevated temperaures are those in which the carbonyl groups are free ofany metallic substituents. Typical indanthrene compounds suitable forthe present purpose include the following:

indanthrene Flavanthrone Pyranthrone Violanthrone3,3'-dichloroindanthrene 3-chloroindanthrene The indanthrene dyes, whichare used as the gelling agents in the subject greases, contain two unitsof the following essential typical grouping per molecule:

middle ring. Others, such as flavanthrene, contain the 1 singleessential carbonyl radical, the tricyclic group being linked to a secondsuch group by means of nitrogen linkages, or (as in the case ofpyranthrone) through unsaturated hydrocarbon linkages Thus, the twotricyclic nuclei may be linked by two N: groups (as in flavanthrone); bytwo NH groups (as in indanthrone blue); by two =CH groups (as inpyranthrone); or by intervening condensed ring systems (as inviolanthrone). Another characteristic of the indanthrone dyes is thatnitrogen is not a nuclear element present in the rings making up theessential tricyclic nuclei.

The lubricating oil chosen to form the greases of invention may beWidely varied. The oil chosen to prepare the grease composition shouldbe capable of performing the lubricating function if it could be used asa liquid. Mineral lubricating oils having a viscosity within the rangeof from about 35 to about 200 SUS at 210 F. may be used for mostapplications. The mineral oil may be of a paraffinic or of a naphthenicnature depending upon the crude source, and ony of the variousdistillates refined by the various refinery techniques are operable.

Synthetic lubricating oils may also be utilized in preparing thelubricating greases of this invention. Synthetic lubricating oils havinga viscosity within the range stated above are operable. These oilsinclude esters of monobasic acids, such as the C Oxo alcohol ester of COxo acid, esters of C Oxo alcohol and octanoic acid, etc.; esters ofdibasic acids, such as di-Z-ethylhexyl sebacate, di-nonyl-adipate, etc.,esters of glycols, e.g., the C Oxo acid diester of tetraethylene glycol,etc., complex esters, such as the complex ester formed by reacting onemol of sebacic acid with two mols of tetraethylene glycol and two molsof 2-ethyl hexanoic acid; other types include complex esters formed byreacting one mol of tetraethylene glycol with two mols of sebacic acidand two mols of 2-ethyl hexanol, complex esters formed by reactingtogether one mol of azelaic acid, one mol of tetraethylene glycol, onemol of C Oxo acid, and the like. A recently developed class, namelydiaryl dialkyl silanes (e.g., diphenyl didodecyl silane) may beemployed. Esters of phosphoric acid may be used, such as the esterformed by contacting three mols of the monomethyl ether of ethyleneglycol with one mol of phosphorus oxychloride. Halocarbon oils, such thepolymers of chlorotrifluorethylene may be employed, as well as alkylsilicon compounds, such as methyl polysiloxanes, ethyl polysiloxanes,methylphenyl polysiloxanes, ethyl-phenyl polysiloxanes, chlorophenylsilicones, and the like. Sulfite esters, such as those formed byreacting one mol of sulfur oxychloride with two mols of the methyl etherof ethylene glycol and the like also are useful, as are carbonates suchas those formed by reacting C Oxo alcohol with ethyl carbonate to form ahalf ester and reacting this half ester with tetraethylene glycol,mercaptals such as those formed by reacting Z-ethylhexyl mercaptan withformaldehyde, formals such as those formed by reacting C Oxo alcoholwith formaldehyde, polyglycols, such as those formed by condensing butylalcohol with up to fifty units of propylene oxide, or mixtures of any ofthe above synthetic oils in an proportions.

on the average.

A recent development in the high temperature lubricating field and inthe allied field of lubrication under conditions of ionizing radiationcomprises the use of polyphenyl ethers as lubricants or as lubricantcomponents. The maximum stability obtained if the polyphenyl ethers areunsubstituted but highly stable lubricants are also prepared whenalpha-cumyl or tertiary-butyl substituents are employed. While ortho,meta or para linkages between phenyl radicals may be utilized, it ispreferred that at least 25% of the ether linkages be in the metaposition relative to each other. As the meta linkage proportionincreases, the pour point of the resulting lubricating oils decreases.It is possible to have, therefore, polyphenyl ethers which are all metalinked but which may instead comprise meta linkages With varyingproportions of ortho or para linkages. It is preferred that thepolyphenyl ether contain from 3 to 6 phenyl radicals per molecule Thecombination of the subject class of thickeners with such lubricants hasbeen found to constitute an outstandingly stable lubricating greaseeither under conditions of temperatures in excess of 350 F. or underconditions of ionizing radiation.

It will be understood that the addition of the amines to the subjectclass of greases may be utilized for the purpose of increasing theconsistency of the grease on the one hand or for decreasing the majorthickener requirements such as dye for a given grease consistency on theother hand. The following examples illustrate the unexpected increase inconsistency of an indanthrene blue (indanthrone) grease, 28% by weightof the grease being indanthrone, the balance of the grease being aresidual petroleum lubricating oil, namely, a bright stock.

Worked strokes penetration, measured with scale cone in a size 0crucible.

According to the data given above, it will be seen that a variety ofamines substantially increase the consistency of the grease whenutilized in proportions between 3 and 15% based on the original greaseformulation.

I claim as my invention:

1. A grease composition comprising a major amount of bright stockmineral lubricating oil gelled to a grease consistency with acombination of 5-35 by weight of indanthrone and 25-20% by weight of adiarylamine having the general configuration H ArN--Ar wherein each Aris an aromatic hydrocarbon radical of the group consisting of phenyl,naphthyl, alkylated phenyl and alkylated naphthyl radicals.

2. A grease composition comprising a major amount of bright stockmineral lubricating oil gelled to a grease consistency with acombination of 5-35% by weight of indanthrone and 25-20% by weight of aphenyl naphthylamine, the amount of said amine being sufiicient tosubstantially increase the consistency of the grease.

3. A grease composition comprising a major amount of bright stockmineral lubricating oil gelled to a grease consistency with acombination of 5-35 by weight of indanthrone and 25-20% by weight of adinaphthylamine;

5 6 the amount of said amine being suificient to substantially 5. Agrease composition according to claim 4 wherein increase the consistencyof the grease. the lubricating oil is a polyphenyl ether.

4. A grease composition comprising a major amount of References Cited inthe file of this Patent a lubricating oil gelled to a grease consistencywith a combination of 5-30% by weight of an indanthrene com- 5 UNITEDSTATES PATENTS pound and 15-20% by weight of a diarylamine having2,351,384 Woods et a1 June 13, 1944 the general configuration 2,403,104Lien July 2, 1946 H 2,663,690 Eckert Dec. 22, 1953 2,848,417 Armstronget a1. Aug. 19, 1958 10 2,851,418 Lyons et a1 Sept. 9, 1958 wherein eachAr is an aromatic hydrocarbon radical of 2,392,776 Lyons et aL June 30,1959 the group consisting of p y nap thyl, al ylat d phenyl 2,908,644 odn et a1 1959 and alkylated naphthyl radicals. 2,946,750 Odell et a1.July 26, 1960

1. A GREASE COMPOSITION COMPRISING A MAJOR AMOUNT OF BRIGHT STOCK MINERAL LUBRICATING OIL GELLES TO A GREASE CONSISTENCY WITH A COMBINATION OF 5-35% BY WEIGHT OF INDANTHRONE AND 2.5-20% BY WEIGHT OF A DIARYLAMINE HAVING THE GENERAL CONFIGURATION 